Yes CW, legally the parent having custody need to have a notorized letter from the other parent stating that this child had permission to travel with this parent. It is really a legal mess that we can blame on these stupid people that take their kids and run off to another country to keep the other parent from seeing him/her. If you are on good terms with your ex then you can do this in a quick and friendly manner, if not, then you really need to see your attorney and let them handle it.
Jim